based on their number. For example, 621 is the first child of 62, who is the second child of 6, who is the sixth child of his parents. In the Henry System, when there are more than nine children, X is used for the 10th child, A is used for the 11th child, B is used for the 12th child, and so on. In the Modified Henry System, when there are more than nine children, numbers greater than nine are placed in parentheses. Henry Modified Henry 1. Progenitor 1. Progenitor 11. Child 11. Child 111. Grandchild 111. Grandchild 1111. Great-grandchild 1111. Great-grandchild 1112. Great-grandchild 1112. Great-grandchild 112. Grandchild 112. Grandchild 12. Child 12. Child 121. Grandchild 121. Grandchild 1211. Great-grandchild 1211. Great-grandchild 1212. Great-grandchild 1212. Great-grandchild 122. Grandchild 122. Grandchild 1221. Great-grandchild 1221. Great-grandchild 123. Grandchild 123. Grandchild 124. Grandchild 124. Grandchild 125. Grandchild 125. Grandchild 126. Grandchild 126. Grandchild 127. Grandchild 127. Grandchild 128. Grandchild 128. Grandchild 129. Grandchild 129. Grandchild 12X. Grandchild 12(10). Grandchild d'Aboville System The d'Aboville System is a descending numbering method developed by Jacques d'Aboville in 1940 that is very similar to the Henry System, widely used in France. It can be organized either by generation or not. It differs from the Henry System in that periods are used to separate the generations and no changes in numbering are needed for families with more than nine children. For example: 1 Progenitor 1.1 Child 1.1.1 Grandchild 1.1.1.1 Great-grandchild 1.1.1.2 Great-grandchild 1.1.2 Grandchild 1.2 Child 1.2.1 Grandchild 1.2.1.1 Great-grandchild 1.2.1.2 Great-grandchild 1.2.2 Grandchild 1.2.2.1 Great-grandchild 1.2.3 Grandchild 1.2.4 Grandchild 1.2.5 Grandchild 1.2.6 Grandchild 1.2.7 Grandchild 1.2.8 Grandchild 1.2.9 Grandchild 1.2.10 Grandchild Meurgey de Tupigny System The Meurgey de Tupigny System is a simple numbering method used for single surname studies and hereditary nobility line studies developed by of the National Archives of France, published in 1953. Each generation is identified by a Roman numeral (I, II, III, ...), and each child and cousin in the same generation carrying the same surname is identified by an Arabic numeral. The numbering system usually appears on or in conjunction with a pedigree chart. Example: I Progenitor II-1 Child III-1 Grandchild IV-1 Great-grandchild IV-2 Great-grandchild III-2 Grandchild III-3 Grandchild III-4 Grandchild II-2 Child III-5 Grandchild IV-3 Great-grandchild IV-4 Great-grandchild IV-5 Great-grandchild III-6 Grandchild de Villiers/Pama System The de Villiers/Pama System gives letters to generations, and then numbers children in birth order.